Participants will take levetiracetam starting at 500 mg daily. If this dose is well tolerated, it will be increased to 500 mg twice a day. Every 3 days, doses may be increased until the target dose of 3000 mg/day is reached. Higher doses, not to exceed 4000 mg/day, may be tried in patients who do not respond fully to the lower doses. Patients and observers will use standard ratings to evaluate the patients' response to therapy during the 8-week study. If, after 8 weeks, the results appear promising, patients may continue treatment for an additional 6 months to evaluate longer-term effects.